The present invention relates generally to the manufacture of electromechanical machines, such as electric motors. More particularly, the invention relates to an improved method and apparatus for producing slot insulators and inserting same into the stator core of an electromechanical machine.
Electric motors and other electromechanical machines are generally constructed having a cylindrical stator core. The inner circumference of the stator core defines a plurality of radial slots in which electrical windings are maintained. A slot insulator, typically referred to as a "slot liner," is located on the inner circumferential surface of each winding slot in order to electrically isolate the windings from the stator core.
During the manufacturing process, individual slot liners are typically inserted into the respective winding slots using automated equipment designed for this purpose. The slot liners themselves have been formed from a roll of insulator material having a width dictated by the axial length of the stator core in which the slot liners are to be inserted. To form individual slot liners, a quantity of material is first drawn from the roll. The material is then cut to a length equivalent to the inner circumferential portion of the winding slot to be insulated. End cuffs are passively formed along the sides of the insulator material as it is pulled from the roll.
For example, consider a stator core having an axial length of 5" and in which each winding slot has an inner circumferential portion of 1.5" to be insulated. According to the prior art described above, it is necessary to use a roll of insulator material having a width of greater than 5" in order to produce slot liners for this core. The insulator material is drawn from the roll, and cut into 1.5" lengths. The insulator blank formed in this manner is bent into a U-shaped slot liner and moved axially into a respective slot.
Typically, a face plate is utilized for slot liner insertion. The face plate defines a plurality of guides in the pattern of the stator core's winding slots. The guides are maintained in register with the end of the stator core as it is indexed to receive the next slot liner.
While the prior art has worked generally well to achieve the formation and insertion of slot liners, it is not without disadvantages. For example, multiple stator lengths may be offered within a single motor size. Thus, it is necessary to maintain in stock rolls of each width that will be required to produce slot liners for all of the various stator lengths.
In addition, the face plate used for slot liner insertion is a relatively complex and expensive part. Moreover, the face plate has a tendency to "grip" the slot liners, often causing the slot liners to be pulled partially from the slots as the stator core is removed from the face plate. When this happens, the slot liners must be manually reinserted into the winding slots.